Rinse all of the vegetables very well and pat dry.
Remove the stems on the cauliflower, chop the head in half, and grate one of the halves using a box grater (note: you can also pulse cauliflower florets in a food processor).
Add cauliflower couscous, cabbage, kale, green onion, dried cranberries, and walnuts to a large serving bowl.
Whisk together the olive oil, lemon juice, and stone ground mustard together in a small bowl. Pour it over the veggies and toss everything together well. Taste the "couscous" for flavor and add more olive oil, lemon juice, and/or sea salt to taste.